Generally, since data currently treated in an electronic circuit disappears with a stop of the current supply resulting from a power failure, battery deterioration, etc., even if it turns ON a power supply again, it cannot resume a process. As a method of solving this, there is a method for backing up stored data to a nonvolatile storage and holding data, when the power supply cutoff is detected. A data hold device and data holding method using a nonvolatile storage device are already disclosed (for example, refer to Patent Literature 1).
In the above-mentioned method, a control device which detects power supply cutoff/turn-on and outputs a signal for request for backup/recovering of data is used toward a controlled system device having a function for performing fixation of the data. Since these control devices process after the power supply cutoff detection, it is necessary to secure another power supply. However, using a battery causes cost increase. In order to solve this problem, “DATA RESTORING METHOD” is proposed as the method of processing by utilizing discharging time of a capacitor (for example, refer to Patent Literature 2).
On the other hand, “PROGRAMMABLE CONTROLLER AND DISPOSAL METHOD AT THE TIME OF POWER OFF FOR THE SAME” for monitoring the power supply lines of two systems (for example, AC 100V side and DC 5V side, etc.) is already disclosed (for example, refer to Patent Literature 3). However, the method disclosed in the Patent Literature 3 does not set up power source monitor time, and is targeted for only at the time of a stop of the device.
Citation List
    Patent Literature 1: Japanese Patent Application Laying-Open Publication No. 2004-186874    Patent Literature 2: Japanese Patent Application Laying-Open Publication No. H06-231053    Patent Literature 3: Japanese Patent Application Laying-Open Publication No. H09-081286